scholarly journals Group theoretical interpretation of the modified gravity in de Sitter space

2016 ◽  
Vol 2016 (3) ◽  
Author(s):  
M. Dehghani
Keyword(s):  
Modified Gravity ◽  
De Sitter Space ◽  
Theoretical Interpretation ◽  
De Sitter

scholarly journals De Sitter field equations from quadratic curvature gravity: A group theoretical approach

2020 ◽  
Vol 35 (19) ◽  
pp. 2050098
Author(s):  
M. Dehghani ◽  
M. R. Setare
Keyword(s):  
Modified Gravity ◽  
Ambient Space ◽  
Theoretical Interpretation ◽  
De Sitter ◽  
Point Function ◽  
Field Equations ◽  
Related Field ◽  
Successful Model ◽  
Massless Spin ◽  
Gauge Fixing

In this paper, the linearized field equations related to the quadratic curvature gravity theory have been obtained in the four-dimensional de Sitter (dS) space–time. The massless spin-2 field equations have been written in terms of the Casimir operators of dS group making use of the ambient space notations. By imposing some simple constraints, arisen from group theoretical interpretation of the field equations, a new four-dimensional Gauss–Bonnet (GB-)like action has been introduced with the related field equations transforming according to the unitary irreducible representations (UIRs) of dS group. Since, the field equations transform according to the UIRs of dS group, the GB-like action, we just obtained, is expected to be a successful model of modified gravity. For more clarity, the gauge invariant field equations have been solved in terms of a gauge-fixing parameter [Formula: see text]. It has been shown that the solution can be written as the multiplication of a symmetric rank-2 polarization tensor and a massless minimally coupled scalar field on dS space. The Krein–Gupta–Bleuler quantization method has been utilized and the covariant two-point function has been calculated in terms of the massless minimally coupled scalar two-point function, using the ambient space notations. It has been written in terms of dS intrinsic coordinates from the ambient space counterpart. The two-point functions are dS invariant and free of any theoretical problems. It means that the proposed model is a successful model of modified gravity and it can produce significant results in the contexts of classical theory of gravity and quantum gravity toy models.

scholarly journals ON EXPONENTIAL MODIFIED GRAVITY

2013 ◽  
Vol 28 (24) ◽  
pp. 1350119 ◽  
Author(s):  
S. I. KRUGLOV
Keyword(s):  
Modified Gravity ◽  
Cosmological Parameters ◽  
De Sitter Space ◽  
De Sitter ◽  
Zero Curvature ◽  
Static Solutions ◽  
Modified Theory Of Gravity ◽  
Jordan And Einstein Frames ◽  
Modified Theory ◽  
Hilbert Action

A modified theory of gravity with the function F(R) = R exp (αR) instead of Ricci scalar R in the Einstein–Hilbert action is considered and analyzed. The action of the model is converted into Einstein–Hilbert action at small value of the parameter α. From local tests we obtain a bound on the parameter α ≤ 10-6 cm 2. The Jordan and Einstein frames are investigated and the potential of the scalar field in Einstein's frame is found. The mass of a scalar degree of freedom as a function of curvature is obtained. The static solutions of the model are found corresponding to the Schwarzschild–de Sitter space. We show that the de Sitter space is unstable but a solution with zero curvature is stable. The cosmological parameters of the model are calculated. It was demonstrated that the model passes the matter stability test.

scholarly journals Gravitational turbulent instability of anti-de Sitter space

2012 ◽  
Vol 29 (19) ◽  
pp. 194002 ◽  
Author(s):  
Óscar J C Dias ◽  
Gary T Horowitz ◽  
Jorge E Santos
Keyword(s):  
De Sitter Space ◽  
De Sitter

scholarly journals Open quantum entanglement: a study of two atomic system in static patch of de Sitter space

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Samim Akhtar ◽  
Sayantan Choudhury ◽  
Satyaki Chowdhury ◽  
Debopam Goswami ◽  
Sudhakar Panda ◽  
...  
Keyword(s):  
Scalar Field ◽  
Density Matrix ◽  
Master Equation ◽  
Quantum Entanglement ◽  
De Sitter Space ◽  
Thermal Bath ◽  
Massless Scalar Field ◽  
De Sitter ◽  
Open Quantum ◽  
Non Locality

Abstract In this work, our prime objective is to study non-locality and long range effect of two body correlation using quantum entanglement from various information theoretic measure in the static patch of de Sitter space using a two body Open Quantum System (OQS). The OQS is described by a system of two entangled atoms, surrounded by a thermal bath, which is modelled by a massless probe scalar field. Firstly, we partially trace over the bath field and construct the Gorini Kossakowski Sudarshan Lindblad (GSKL) master equation, which describes the time evolution of the reduced subsystem density matrix. This GSKL master equation is characterized by two components, these are-Spin chain interaction Hamiltonian and the Lindbladian. To fix the form of both of them, we compute the Wightman functions for probe massless scalar field. Using this result alongwith the large time equilibrium behaviour we obtain the analytical solution for reduced density matrix. Further using this solution we evaluate various entanglement measures, namely Von-Neumann entropy, R$$e'$$e′nyi entropy, logarithmic negativity, entanglement of formation, concurrence and quantum discord for the two atomic subsystem on the static patch of De-Sitter space. Finally, we have studied violation of Bell-CHSH inequality, which is the key ingredient to study non-locality in primordial cosmology.

scholarly journals Probing Planckian physics in de Sitter space with quantum correlations

2014 ◽  
Vol 351 ◽  
pp. 872-899 ◽  
Author(s):  
Jun Feng ◽  
Yao-Zhong Zhang ◽  
Mark D. Gould ◽  
Heng Fan ◽  
Cheng-Yi Sun ◽  
...  
Keyword(s):  
De Sitter Space ◽  
Quantum Correlations ◽  
De Sitter
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